McDonald’s old fries were fried in beef lard.
They used to spend less on fry oil because it came from frying fatty hamburger, the fries were fried in a mix of beef grease (lard) and the usual suspects.
Once they removed the lard every restaurant freely generated the fries changed flavor
Lard is pork fat. McDonald's used a frying mixture that was mostly beef tallow. Not that it's healthy in any way, but beef fat tends to be relatively high in monounsaturated fats. It didn't come from reusing burger drippings. That stuff is almost always scraped off into grease collectors and can't really be reused. My understanding is that beef fat cooked to griddle temperature is likely going to burn if reused in a deep fryer.
The mixture was made from rendered beef suet because their supplier at the time couldn't afford the equipment to make hydrogenated vegetable oils. I'm pretty sure that over time, McDonald's needed multiple suppliers and could have switched to vegetable oil at any time, but the fries were great.
In the beginning, the McDonald brothers had one hamburger stand, and they bought their fry oil from Interstate. At the time, partially hydrogenated vegetable oil was the preferred frying oil, but hydrogenation equipment was too expensive for Interstate’s tiny operation. By providing clients with a blend of about 7% vegetable oil and 93% beef tallow, they could extend the oil’s shelf life without the use of costly machinery. McDonald’s irresistibly crispy, flavorful french fries? Simply a byproduct of frugal savvy.
Ray Kroc, the salesman who would become the founder of the McDonald’s franchise, fell in love with this beef tallow–fried version in 1954. Imagining the treat replicated across the country, Kroc bought the restaurant’s franchise rights. He became a master of the french fry, developing potato curing methods and a “potato computer” to perfect cooking time.
